11
J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015 © 2015, TextRoad Publication ISSN: 2090-4274 Journal of Applied Environmental and Biological Sciences www.textroad.com Corresponding author: A. Sadeghian - Department of Mathematics, Islamic Azad University of Yazd, Yazd, Iran. [email protected] Numerical Solution of Fractional Telegraph Equation Using the Second Kind Chebyshev Wavelets Method A. Sadeghian * 1 , M. H. Heydari 2 , M. R. Hooshmandasl 3 and S. M. Karbassi 4 1,4 Department of Mathematics, Islamic Azad University of Yazd, Yazd, Iran 2,3,4 Faculty of Mathematics, Yazd University, Yazd, Iran Received: March 26, 2014 Accepted: May 17, 2015 ABSTRACT In this paper, the two-dimensional second kind Chebyshev wavelets are applied for numerical solution of the time-fractional telegraph equation with Dirichlet boundary conditions. In this way, a new operational matrix of fractional derivative for the second wavelets is derived and then this operational matrix has been employed to obtain the numerical solution of the above mentioned problem. The main characteristic behind this approach is that it reduces such problems to those of solving a system of algebraic equations which greatly simplifying the problem. The power of this manageable method is illustrated. KEYWORDS:Second kind Chebyshev wavelet, Telegraph equation, Dirichlet boundary condition, Fractional derivative. 1. INTRODUCTION In recent years, fractional calculus and differential equations have found enormous applications in mathematics, physics, chemistry and engineering because of this fact that, a realistic modeling of a physical phenomenon having dependence not only at the time instant, but also the previous time history can be successfully achieved by using fractional calculus. The application of the fractional calculus have been demonstrated by many authors. For examples, it is applied to model the nonlinear oscillation of earthquakes [1], fluid-dynamic traffic [2], frequency dependent damping behavior of many viscoelastic materials [3], continuum and statistical mechanics [4], colored noise [5], solid mechanics [6], economics [7], signal processing [8], and control theory [9]. However, during the last decade fractional calculus has attracted much more attention of physicist and mathematicians. Due to the increasing applications, some schemes have been proposed to solve fractional differential equations. The most frequently used methods are Adomian decomposition method (ADM) [10-12], homotopy perturbation method [13], homotopy analysis method [14], Variational iteration method (VIM) [15, 16], Fractional differential transform Method (FDTM) [17-22], Fractional difference method (FDM) [23], power series method [24], generalized block pulse operational matrix method [25] and Laplace transform method [26]. Also, recently the operational matrices of fractional order integration for the Haar wavelet [27], Legendre wavelet [28] and the Chebyshev wavelets of first kind [29, 30] and second kind [31] have been developed to solve the fractional differential equations. In this paper consider the time-fractional telegraph equation of order 2) < (1 α α as: [0,1]. [0,1] ) , ( ), , ( ) , ( = ) , ( ) , ( ) , ( 2 2 1 1 × + + + - - t x t x f t x u x t x u t x u t t x u t α α α α (1) where β β t denotes the Caputo fractional derivative of order β , that will be described in the next section. This equation is commonly used in the study of wave propagation of electric signals in a cable transmission line and also in wave phenomena. This equation has been also used in modeling the reaction-diffusion processes in various branches of engineering sciences and biological sciences by many researchers (see [32] and references therein). The main purpose of this paper is to apply the second kind Chebyshev wavelets for solving time-fractional telegraph equation (1). In this way, we first describe some properties of the second kind Chebyshev polynomials and Chebyshev wavelets. Then, a new operational matrix of fractional derivative for the second kind Chebyshev wavelets are derived and are applied to obtain approximate solution for the under study problem. This paper is organized as follows: In Section 2, some necessary definitions of the fractional calculus are reviewed. In Section 3, the second kind Chebyshev polynomials and the second kind Chebyshev wavelets with some useful theorems are investigated. In Section 4, the proposed method is described. In Section 5, some numerical examples are presented. Finally a conclusion is drawn in Section 6. 64

Numerical Solution of Fractional Telegraph …. Appl. Environ. Biol. Sci., 5...Numerical Solution of Fractional Telegraph Equation Using the Second Kind Chebyshev Wavelets Method A

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J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015

© 2015, TextRoad Publication

ISSN: 2090-4274 Journal of Applied Environmental

and Biological Sciences

www.textroad.com

Corresponding author: A. Sadeghian - Department of Mathematics, Islamic Azad University of Yazd, Yazd, Iran. [email protected]

Numerical Solution of Fractional Telegraph Equation Using the Second Kind

Chebyshev Wavelets Method

A. Sadeghian* 1 , M. H. Heydari2

, M. R. Hooshmandasl3

and S. M. Karbassi4

1,4

Department of Mathematics, Islamic Azad University of Yazd, Yazd, Iran 2,3,4

Faculty of Mathematics, Yazd University, Yazd, Iran Received: March 26, 2014

Accepted: May 17, 2015

ABSTRACT

In this paper, the two-dimensional second kind Chebyshev wavelets are applied for numerical solution of the time-fractional

telegraph equation with Dirichlet boundary conditions. In this way, a new operational matrix of fractional derivative for the

second wavelets is derived and then this operational matrix has been employed to obtain the numerical solution of the above

mentioned problem. The main characteristic behind this approach is that it reduces such problems to those of solving a system

of algebraic equations which greatly simplifying the problem. The power of this manageable method is illustrated.

KEYWORDS:Second kind Chebyshev wavelet, Telegraph equation, Dirichlet boundary condition, Fractional derivative.

1. INTRODUCTION

In recent years, fractional calculus and differential equations have found enormous applications in mathematics, physics,

chemistry and engineering because of this fact that, a realistic modeling of a physical phenomenon having dependence not only

at the time instant, but also the previous time history can be successfully achieved by using fractional calculus. The application

of the fractional calculus have been demonstrated by many authors. For examples, it is applied to model the nonlinear

oscillation of earthquakes [1], fluid-dynamic traffic [2], frequency dependent damping behavior of many viscoelastic materials

[3], continuum and statistical mechanics [4], colored noise [5], solid mechanics [6], economics [7], signal processing [8], and

control theory [9]. However, during the last decade fractional calculus has attracted much more attention of physicist and

mathematicians. Due to the increasing applications, some schemes have been proposed to solve fractional differential

equations. The most frequently used methods are Adomian decomposition method (ADM) [10-12], homotopy perturbation

method [13], homotopy analysis method [14], Variational iteration method (VIM) [15, 16], Fractional differential transform

Method (FDTM) [17-22], Fractional difference method (FDM) [23], power series method [24], generalized block pulse

operational matrix method [25] and Laplace transform method [26]. Also, recently the operational matrices of fractional order

integration for the Haar wavelet [27], Legendre wavelet [28] and the Chebyshev wavelets of first kind [29, 30] and second kind

[31] have been developed to solve the fractional differential equations.

In this paper consider the time-fractional telegraph equation of order 2)<(1 ≤αα as:

[0,1].[0,1]),(),,(),(=),(),(),(2

2

1

1

×∈+∂

∂+

∂+

txtxftxux

txutxut

txut α

α

α

α

(1)

where β

β

t∂

∂ denotes the Caputo fractional derivative of order β , that will be described in the next section. This equation is

commonly used in the study of wave propagation of electric signals in a cable transmission line and also in wave phenomena.

This equation has been also used in modeling the reaction-diffusion processes in various branches of engineering sciences and

biological sciences by many researchers (see [32] and references therein).

The main purpose of this paper is to apply the second kind Chebyshev wavelets for solving time-fractional telegraph

equation (1). In this way, we first describe some properties of the second kind Chebyshev polynomials and Chebyshev

wavelets. Then, a new operational matrix of fractional derivative for the second kind Chebyshev wavelets are derived and are

applied to obtain approximate solution for the under study problem. This paper is organized as follows: In Section 2, some

necessary definitions of the fractional calculus are reviewed. In Section 3, the second kind Chebyshev polynomials and the

second kind Chebyshev wavelets with some useful theorems are investigated. In Section 4, the proposed method is described.

In Section 5, some numerical examples are presented. Finally a conclusion is drawn in Section 6.

64

Sadeghian et al.,2015

2. Basic definitions In the development of theories of fractional derivatives and integrals, many definitions for fractional derivatives and integrals

are appeared, such as Riemann-Liouville and Caputo [33], which are described below:

Definition 2-1

A real function 0> ),( xxu , is said to be in the space R∈µµ

,C if there exists a real number )(> µp such that

)(=)(1xuxxu

p, where ][0,)(

1∞∈Cxu and it is said to be in the space

n

if N∈∈ nCun

,

)(

µ.

Definition 2-2

The Riemann-Liouville fractional integration operator of order 0≥α of a function 1 , −≥∈ µµ

Cu , is defined as [33]:

( )

Γ−

∫0.=),(

0,>,)()()(

1

=)(1

0

α

α

α

α

α

xu

dttutxxuI

x

(2)

It has the following properties:

( ) ( ) ,1)(

1)(=),(=)( ϑαϑαβαβα

ϑα

ϑ++

++Γ

+ΓxxIxuIxuII (3)

where 0, ≥βα and 1> −ϑ .

Definition 2-3

The fractional derivative operator of order 0>α in the Caputo sense is defined as [33]:

( )

−−−Γ

−−

∫ .<<1,)()()(

1

,=,)(

=)()(1

0nndttutx

n

ndx

xud

xuDnn

x

n

n

α

α

α

α

α

N

(4)

where n is an integer, 0>x , and n

Cu1

∈ .

The useful relation between the Riemann-Liouvill operator and Caputo operator is given by the following expression:

( ) ,<10,>,!

)(0)(=)()(

1

0=

nnxj

xuxuxuDI

j

jn

j

≤−−+

∗ ∑ ααα

(5)

where n is an integer, 0>x , and n

Cu1

∈ .

For more details about fractional calculus see [33].

3. The second kind Chebyshev polynomials and wavelets

The well-known second kind Chebyshev polynomial )(zUm

form a complete set of orthogonal functions with respect to the

weight function 21=)( zzw − on the interval 1,1][− . They can be determined with the aid of the following recurrence

formula [34]:

,2,3,=),()(2=)(21

KnzUzzUzUmmm −−

with 1=)(0zU and zzU 2=)(

1. For practical use of these polynomials on the interval of interest [0,1] , it is necessary to

shift the defining domain by means of the following substitution:

1.01,2= ≤≤− xxz

So, the shifted second kind Chebyshev polynomials )(xUm

are obtained on the interval [0,1] as 1)(2=)( −

xUxUmm

. The orthogonality condition for these shifted polynomials is:

,4

=1)(21)()(2

1

0mnnm

dxxxUxU δπ

−−

∗∗

∫ (6)

where mn

δ is the Kroneker delta.

The analytic form of the shifted second kind Chebyshev polynomial is:

65

J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015

,=)(0=

mi

m

i

maxU ∑

(7)

where

.1)!(2)!(

1)!2(1)(=

2

i

i

im

mix

iim

ima

+−

++−

(8)

The second kind Chebyshev wavelets ),,,(=)( xmnkxnm

ψψ , which is constructed from it's corresponding polynomials

involve four arguments, k

n ,21,= K , k is assumed any positive integer, m is the degree of the second kind Chebyshev

polynomials and the variable x is defined over [0,1] . They are defined on the interval [0,1] as [31]:

−∈+−+

+

..0,

],2,

2

1[1),2(22

2=)(

12

1

wo

nnxnxU

x kk

k

m

k

nm πψ (9)

We should note that in dealing with the second kind Chebyshev wavelets the weight function 1)(2=)( −

xwxw have to

be dilate and translate as 1)2(2=)( 1+−

+

nxwxwk

n.

A function )(xu defined on [0,1] may be expanded by the second kind Chebyshev wavelets as:

),(=)(0=1=

xcxunmnm

mn

ψ∑∑∞∞

(10)

where n

wnmnmxxuc ))(),((= ψ , and (.,.) denotes the inner product in [0,1]

2

nw

L .

If the infinite series in (10) is truncated, then it can be written as:

),(=)()(1

0=

2

1=

xCxcxuT

nmnm

M

m

k

n

Ψ∑∑−

ψ; (11)

where C and )(xΨ are Mmk

2=ˆ column vectors given by:

[ ] ,,,|,|,,,|,,,= ˆ11)(22121

T

mM

kMMMcccccccC KKKK

+−+

and

[ ] ,)(,),(|,|,)(,),(|)(,),(=)( ˆ11)(2211

T

mM

kMMMxxxxxxx ΨΨΨΨΨΨΨ

+−+

KKKK (12)

in which nmicc = , )(=)( xx

nmiψΨ . The index i , is determined by the relation 11)(= ++− mMni .

Similarly, an arbitrary function of two variables ),( txu defined over [0,1][0,1]× , may be expanded into second kind

Chebyshev wavelets basis as:

),()(=)()(),(ˆ

1=

ˆ

1=

tUxyxutxuT

jiij

m

j

m

i

ΨΨ∑∑ ψψ; (13)

where ][=ijuU and ( )( ))(),,(),(= ttxuxu

jiijψψ .

4. The operational matrix of fractional derivative

Here, we present a procedure to derive the operational matrix of fractional derivative in the Caputo sense for the second kind

Chebyshev wavelets.

Remark 1 By using the shifted second kind Chebyshev polynomials, any component )(xnm

ψ of (12) can be written as:

),()(222

=)(I

2

1

xnxUxnk

k

m

k

nmχ

πψ −

+

where ]2

1,

2[=I

kknk

nn +

, 1,0,1,=1,,20,= −− Mmnk

KK and )(I

xnk

χ is the characteristic function defined as:

66

Sadeghian et al.,2015

+∈

..0,

],2

1,

2[1,

=)(I

wo

nn

x

x

kk

nk

χ

Next we present a useful theorem about fractional derivative of the second kind Chebyshev wavelets:

Lemma 4-1 Let )(xnm

ψ be a component of (12) defined on the interval nkI , and )(xD

nmψ

α

∗ be fractional derivative of

order )<<1(0> − αααα , of )(xnm

ψ with respect to x . Then for any 1,20,1,= −

kn K , we have:

≥Ω+Ω

∑∑∑−−

+

∗,),(),(ˆ)(),(

,<00,

=)( )(1

0=

12

1=

)(1

0=

αψψ

α

ψαα

α

mxjmxjm

m

xD lj

nM

j

k

nl

nj

nM

j

nm

where

,3)(1)()(1)!(2)!(

)2

3()(1)!()!1)((1)(2

=),(

1)2(

=

)(

+−+Γ+−Γ−Γ+−

+−Γ+−Γ+++−

Ω

−+++

∑αααπ

ααα

α

α

ijiiiim

iijimij

jm

ijmikm

i

n

and

,)())(2(1)()(

)!(2=),(ˆ 2

1

20=

21)(

=

)( dxxwlxxfbi

ibjm l

rk

ik

l

k

ljr

j

r

mi

ikm

i

n ∗+++

−×+−Γ−Γ

Ω ∫∑∑αααπ

α

α

mib and

jrb are defined in (8) and

).()(

)2

(=)(

,1]2

1[1

2

1

2

xdssx

ns

xfk

n

i

kk

n

k

ni ++−

−+

∫ χαα

α

Proof. For α<m , from definitions of the shifted second kind Chebyshev polynomials and Caputo's derivative the

statement is clear. For ≥ αm , from remark (1) and analytic form of the shifted second kind Chebyshev polynomials we

have:

).()(222

=)(I

0=

2

1

xnxbxnk

ik

mi

m

i

k

nmχ

πψ −∑

+

(14)

We notice that this function is zero outside the interval ]2

1,

2[

kk

nn +

. Now by applying α

∗D on both sides of (14) we get:

)(I

=

)(I

0=

)2

(1)(

)!(=)

2(=)(

xnk

i

k

mi

m

i

xnk

i

kmi

m

i

nm

nx

i

ianxDaxD χ

αχψ

α

α

αα −

∗∗ −

+−Γ

− ∑∑

),(1)()(

)!(

=

xfi

iai

mi

m

i +−Γ−Γ+ ∑

αααα

(15)

where

).()(

)2

(=)(,

2=

,1]2

1[1

2

1

2

)2

3(

xdssx

ns

xfb

ak

n

i

kk

n

k

ni

mi

ik

mi ++−

−++

∫ χπ

αα

α

67

J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015

Here, due to the fact that )(I)2

(x

nk

i

k

n

x χα−

− is zero outside the interval ]2

1,

2[

kk

nn +

, then, the second kind Chebyshev

wavelets expansion of this function has only components of basis Chebyshev wavelets )(xΨ that are non-zero on this

interval which yields:

,,1,,=),(=)2

(1

0=

)(I mixen

x njij

M

j

xnk

i

kK+− ∑

ααψχα

(16)

where

dxxwnxb

dxxwxn

xe n

irkk

n

k

nik

jr

k

j

r

nnj

i

k

k

n

k

nij )()(22

2=)()()

2(= 2

1

2

)(

2

2

0=

2

1

2

∗−+

+

+

∗−

+

−− ∫∑∫α

α

α

πψ

,3)(

)2

3(

2

2=

)2

1(

0= +−+Γ

+−+Γ

+−

∑α

α

α ri

rib

ik

jrj

r

(17)

and ( )21)2(21=)( −−−

nxxwk

n.

Also, expanding )(xfi

by the second kind Chebyshev wavelets in each of the intervals 1,21,=,)(I −+k

xlk

nl Kχ , yields:

),(ˆ=)(1

0=

xexf ljij

M

j

i ψ∑−

(18)

where

.)())(2(2

=)()()(=ˆ 2

1

2

2

2

0=

2

1

2

dxxwlxxfb

dxxwxxfe l

rk

ik

l

k

l

jr

k

j

r

lljik

l

k

lij

+

+

+

−∫∑∫π

ψ (19)

Now by substituting (16)-(19) into (15), we obtain:

),(),(ˆ)(),(=)( )(1

0=

12

1=

)(1

0=

xjmxjmxD lj

nM

j

k

nl

nj

nM

j

nm ψψψαα

α Ω+Ω ∑∑∑−−

+

∗ (20)

where mji

m

i

njm ΘΩ ∑ αα =

)(=),( and

mji

m

i

njm ΘΩ ∑

ˆ=),(ˆ=

)(

αα

, and

,3)(

)2

3(

2

2

1)(

)!(=

)2

1(

0= +−+Γ

+−+Γ

×+−Γ

Θ+−

∑α

α

α α ri

rib

i

ia

ik

jrj

r

mimji

and

.)())(2(2

1)()(

)!(=ˆ 2

1

2

2

1

0=

dxxwlxxfb

i

ial

rk

ik

l

k

l

jr

k

j

r

mimji

+

+

−×+−Γ−Γ

Θ ∫∑πααα

After some simplification, mji

Θ and mji

Θ can be expressed in the following form:

,,3)(1)()(1)!(2)!(

)2

3()(1)!()!1)((1)(2

=

1)2(

≥+−+Γ+−Γ−Γ+−

+−Γ+−Γ+++−Θ

−+++

α

αααπ

ααα

mijiiiim

iijimijijmik

mji

and

.,)())(2(1)()(

)!(2=ˆ 2

1

20=

21)(

≥−×+−Γ−Γ

Θ ∗

+++

∫∑ ααααπ

mdxxwlxxfbi

ibl

rk

ik

l

k

ljr

j

r

mi

ik

mji

Therefore (20) can be written as:

68

Sadeghian et al.,2015

)(1)],(,,1),(,0),([=)( )()()(xMmmmxD

n

nnn

nmΨ−ΩΩΩ

∗ ααα

α

ψ K

),(1)],(ˆ,,1),(ˆ,0),(ˆ[)()()(

12

1=

xMmmml

nnn

k

nl

Ψ−ΩΩΩ+ ∑−

+

αααK (21)

where

1.,20,1,=)],(,),(),([=)( 1)(10 −Ψ−

k

Msssssxxxx KK ψψψ

This completes the proof.

Remark 2 For αα = , from Caputo's derivative, we have:

≥Ω

∑−

∗.),(),(

,<00,

=)()(

1

0=

αψ

α

ψα

α

mxjm

m

xD nj

nM

j

nm

Theorem 4-2 Let )(xΨ be the second kind Chebyshev wavelets vector defined in (12) and )<<1(0> − αααα ,

be a positive constant. Then we have:

),(=)( xDxD ΨΨ∗

αα

(22)

where αD is the mm ˆˆ × operational matrix of fractional derivative of order α of the second kind Chebyshev wavelet and

is defined as follows:

,

000

00

0

=

α

αα

ααα

αααα

α

B

FB

FFB

FFFB

D

K

K

MMOMM

K

K

(23)

where α

B and αF are MM × matrices given by:

,

1)1,(1,1)(1,0)(

1)1,(1,1)(1,0)(

1),(,1)(,0)(

000

000

=

)()()(

)()()(

)()()(

−−Ω−Ω−Ω

−+Ω+Ω+Ω

−ΩΩΩ

MMMM

M

MB

nnn

nnn

nnn

ααα

ααα

αααα

ξξξ

ξξξ

K

MKMM

K

K

K

MKMM

K

(24)

and

69

J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015

,

1)1,(ˆ1,1)(ˆ1,0)(ˆ

1)1,(ˆ1,1)(ˆ1,0)(ˆ

1),(ˆ,1)(ˆ,0)(ˆ

000

000

=

)()()(

)()()(

)()()(

−−Ω−Ω−Ω

−+Ω+Ω+Ω

−ΩΩΩ

MMMM

M

MF

nnn

nnn

nnn

ααα

ααα

αααα

ξξξ

ξξξ

K

MKMM

K

K

K

MKMM

K

(25)

and αξ = .

Proof. It is an immediate consequence of the lemma 4.1.

Remark 3 From remark 2, it must be noted that for αα = , we have 0=α

F .

5. Description of the proposed method In this section, we apply the operational matrix of fractional derivative for second kind Chebyshev wavelet for solving

fractional telegraph equation (1) with the boundary conditions:

).(=)(1,),(=,1)(

),(=)(0,),(=,0)(

11

00

tgtuxfxu

tgtuxfxu (26)

For this purpose, we suppose:

),()(=),( tUxtxuT

ΨΨ (27)

where mmji

uU ˆˆ, ][=×

is an unknown matrix which should be found and (.)Ψ is the vector which is defined in (12). Now

using (13) and (22), we obtain:

),()(=),( tUDxtxut

TΨΨ

∂α

α

α

(28)

),()(=),( 1

1

1

tUDxtxut

T ΨΨ∂

∂−

α

α

α

(29)

and

).())((=),(2

2

2

tUxDtxux

TΨΨ

∂ (30)

Also using (13), the function ),( txf in (1) can be approximated as:

),()(),( tBxtxf TΨΨ; (31)

where ][=ij

BB is a mm ˆˆ × known matrix with entries ( )( ))(),,(),(= ttxfxBjiij

ψψ . Substituting (27)-(31) in (1)

consequent:

[ ] 0.=)()()()( 21tBUDUDDUx

TTΨ−−++Ψ

−αα

(32)

The entries of vectors )(xΨ and )(tΨ in (32) are independent, so we have:

0.=)()(= 21BUDUDDUH

T−−++

−αα

(33)

Here, we choose 22)ˆ( −m equations of (33) as:

1.ˆ,2,=,0,= −mjiHij

K (34)

We can also approximate the functions )(0 xf , )(1xf , )(

0tg and )(

1tg as:

70

Sadeghian et al.,2015

),(=)(),(=)(

),(=)(),(=)(

4121

3010

tCtgxCxf

tCtgxCxfTT

TT

ΨΨ

ΨΨ (35)

where 1

C , 2

C , 3C and 4

C are known vectors of dimension m .

Applying (27) and (35) in the boundary conditions (26), we have:

).(=)((1),)(=(1))(

),(=)((0),)(=(0))(

42

31

tCyUCxUx

tCyUCxUxTTTT

TTTT

ΨΨΨΨΨΨ

ΨΨΨΨΨΨ (36)

The entries of vectors )(xΨ and )(tΨ are independent, so from (36) we obtain:

0.=(1)=0,=(1)=

0,=(0)=0,=(0)=

4422

3311

TT

TT

CUCU

CUCU

−ΨΛ−ΨΛ

−ΨΛ−ΨΛ (37)

By choosing the m equations of 1,2)=( 0= jj

Λ and 2ˆ −m equations of 3,4)=( 0= jj

Λ , we get 4ˆ4 −m

equations, i.e.

1.ˆ,2,3,=3,4,=0,=

,ˆ,1,2,=1,2,=0,=

−Λ

Λ

mij

mij

ji

ji

K

K

(38)

Equetion (34) together (38) give 2

m equations, which can be solved for iju , mji ˆ,1,2=, K . So the unknown function

),( txu can be found.

6 . Numerical examples In this section, we demonstrate the efficiency of the proposed method for numerical solution of the telegraph equation in

the form of (1) with the boundary conditions (26).

Example 1 Consider the time-fractional telegraph equation (1) with 1=),( 2−+ txtxf and the boundary conditions

as:

.1=)(1,,1=,1)(

,=)(0,,=,0)(2

2

ttuxxu

ttuxxu

++

The exact solution of this problem for 2=α is txtxu +2=),( . Numerical solutions for some different values of α and

[0,1]∈t for 3)=1,=(6=ˆ Mkm are shown in Fig. 1. The values of exact solution ( 2=α ) and approximate solutions

for some different values of α and some nodes ),( yx in [0,1][0,1]× , for 6=m are shown in Table 1.

Table1.Comparison between the exact ( 2=α ) and numerical solutions for Example ??.

),( ii yx 1.4=α 1.6=α 1.8=α Exact solution

(0.2,0.2) 0.26551095384623 0.25900735191924 0.25037754779349 0.24000000000000

(0.4,0.4) 0.61739964615400 0.60276654181831 0.58334948253535 0.56000000000000

(0.6,0.6) 1.01739964615401 1.00276654181831 0.98334948253536 0.96000000000000

(0.8,0.8) 1.46551095384624 1.45900735191925 1.45037754779350 1.44000000000000

(1.0,1.0 1.99999999999999 1.99999999999999 1.99999999999999 2.00000000000000

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J. Appl. Environ. Biol. Sci., 5(9S)64-74, 2015

Fig.1.Numerical solutions of Example 1 for some different values of α .

Example 2 Consider time-fractional telegraph equation (1) with 0=),( txf and the boundary conditions as:

.=)(1,,=,1)(

,=)(0,,=,0)(11 tx

tx

etuexu

etuexu

−−

The exact solution of this problem for 2=α is tx

etxu−=),( . Numerical solutions for some different values of α and

[0,1]∈t for 4)=1,=(8=ˆ Mkm are shown in Fig. 2. The values of the exact solution ( 2=α ) and approximate

solutions for some different values of α and some nodes ),( yx in [0,1][0,1]× , for 8=m are shown in Table 2.

Table 2.Comparison between the exact ( 2=α ) and numerical solutions for Example 2.

),(iiyx

1.4=α

1.6=α

1.8=α

Exact solution

(0.2,0.2)

1.00325555517139 1.00391875185692 1.00627606867049 1.00000000000000

(0.4,0.4)

1.00541907760911 1.00685195815738 1.01150179716283 1.00000000000000

(0.6,0.6)

1.00546382142790 1.00673580015166 1.01056465711498 1.00000000000000

(0.8,0.8)

1.00334917683010 1.00379783774964 1.00506051184037 1.00000000000000

(1.0,1.0

0.99944928830814 0.99944928830812 0.99944928830815 1.00000000000000

72

Sadeghian et al.,2015

Fig.2.Numerical solutions of Example 2 for some different values of α .

Conclusion In this paper, a numerical method for approximating the solution of the time-fractional telegraph equation with Dirichlet

boundary condition by combining second kind Chebyshev wavelet function with their operational matrix of fractional

derivatives was presented. The method was shown that is very convenient for solving boundary value problems. Also, the

implementation of the proposed method is very simple and is very efficient for solution of the telegraph problem. Moreover, the

proposed method can be used for numerical solution of other kinds of fractional partial differential equations such as Poisson

and diffusion equations.

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